Stegosaurus Fossil range: Late Jurassic
Model Stegosaurus, Bałtów Jurassic Park, Poland. The Late Jurassic (or Malm) Epoch of the Jurassic Period is the unit of geologic time from 161
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Sauropsida Superorder: Dinosauria Order: Ornithischia Suborder: Thyreophora Infraorder: Stegosauria Family: Stegosauridae Genus: Stegosaurus Marsh, 1877
Species
S. Chordates ( Phylum Chordata) are a group of Animals that includes the Vertebrates together with several closely related Invertebrates Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Ornithischia (ɔrnɪˈθɪskiə) or Predentata is an extinct order of beaked herbivorous Dinosaurs The name ornithischia The Thyreophora ("shield bearers" often known simply as "armored dinosaurs" - Greek: θυρεος, a large oblong shield like a door and Known colloquially as stegosaurs the Stegosauria are a group of herbivorous Dinosaurs of the Jurassic and Early Cretaceous Periods Known colloquially as stegosaurs the Stegosauria are a group of herbivorous Dinosaurs of the Jurassic and Early Cretaceous Periods Othniel Charles Marsh ( October 29, 1831 &ndash March 18, 1899) was one of the pre-eminent Paleontologists of the 19th century who In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. armatus Marsh, 1877 (type) S. In Taxonomy, a type species is the species that originally defined a genus. stenops Marsh, 1887 S. longispinus Gilmore, 1914

Stegosaurus (IPA: /ˌstɛgəˈsɔrəs/) is a genus of stegosaurid armoured dinosaur from the Late Jurassic period (Kimmeridgian to Early Tithonian) in what is now western North America. Charles Whitney Gilmore (1874-1945 was an American paleontologist, who named Dinosaurs in North America and Mongolia, including the A genus (plural genera from Γένος Latin genus "descent family type gender" is a low-level Taxonomic Known colloquially as stegosaurs the Stegosauria are a group of herbivorous Dinosaurs of the Jurassic and Early Cretaceous Periods The Thyreophora ("shield bearers" often known simply as "armored dinosaurs" - Greek: θυρεος, a large oblong shield like a door and The Late Jurassic (or Malm) Epoch of the Jurassic Period is the unit of geologic time from 161 The Kimmeridgian is a stage of the Late Jurassic Epoch. It spans the time between 155 The Tithonian is the final stage of the Late Jurassic Epoch. It spans the time between 150 In 2006, a specimen of Stegosaurus was announced from Portugal, suggesting that they were present in Europe as well. Portugal, officially the Portuguese Republic (República Portuguesa is a country on the Iberian Peninsula. ^[1] Due to its distinctive tail spikes and plates, Stegosaurus is one of the most recognizable dinosaurs, along with Tyrannosaurus, Triceratops, and Apatosaurus. The thagomizer, or tail spikes, is an arrangement of four to ten spikes on the tails of particular Dinosaurs of the clade Stegosauria, of Tyrannosaurus ( or, meaning 'tyrant lizard' is a Genus of Theropod Dinosaur. Triceratops (traɪˈsɛrətɒps is an extinct Genus of herbivorous ceratopsid Dinosaur which lived during the late Maastrichtian The name Stegosaurus means "roof-lizard" and is derived from the Greek στέγος-, stegos- ("roof") and σαῦρος, -sauros ("lizard"). The Ancient Greek language is the historical stage in the development of the Hellenic language family spanning the Archaic (c ^[2] At least three species have been identified in the upper Morrison Formation and are known from the remains of about 80 individuals. The Morrison Formation is a distinctive sequence of Late Jurassic Sedimentary rock that is found in the western United States which has been the most fertile source They lived some 155 to 145 million years ago, in an environment and time dominated by the giant sauropods Diplodocus, Camarasaurus, and Apatosaurus. In Astronomy, Geology, and Paleontology, mya or " mya " is an abbreviation for "million years ago". Sauropoda (sɔˈrɒpədə or the sauropods (/ˈsɔroʊpɒd/ are a suborder or infraorder of the Saurischian ("lizard-hipped" Diplodocus (dɪˈplɒdəkəs /daɪˈplɒdəkəs/ Diplodocus is among the most easily identifiable dinosaurs with its classic dinosaur shape long neck Camarasaurus (ˌkæmərəˈsɔrəs KAM-uh-ruh-SAWR-us meaning 'chambered lizard' referring to the holes in its Vertebrae ( Greek καμαρα

A large, heavily built, herbivorous quadruped, Stegosaurus had a distinctive and unusual posture, with a heavily arched back, short forelimbs, head held low to the ground and a stiffened tail held high in the air. Herbivory is a form of Predation in which an Organism, known as a herbivore, consumes principally Autotrophs ref name=Campbell>Campbell Quadrupedalism (from Latin meaning "four legs" is a form of land animal locomotion using four legs. Its array of plates and spikes have been the subject of much speculation. The spikes were most likely used for defense, while the plates have also been proposed as a defensive mechanism, as well as having display and thermoregulatory (heat control) functions. Thermoregulation is the ability of an Organism to keep its body temperature within certain boundaries even when temperature surrounding is very different Stegosaurus was the largest of all the stegosaurians (bigger than genera such as Kentrosaurus and Huayangosaurus) and, although roughly bus-sized, it nonetheless shared many anatomical features (including the tail spines and plates) with the other stegosaurian genera. Known colloquially as stegosaurs the Stegosauria are a group of herbivorous Dinosaurs of the Jurassic and Early Cretaceous Periods Kentrosaurus (meaning "pointed lizard" ˌkɛtroʊˈsɔrəs KEN-troe-SAW-rus, from the Greek kentron/κεντρον Huayangosaurus is a Genus of Stegosaurian Dinosaur from the Middle Jurassic of China.

Description

The size of a Stegosaurus compared to a human.

Averaging around 9 metres (30 ft) long and 4 metres (14 ft) tall, the quadrupedal Stegosaurus is one of the most easily identifiable dinosaurs, due to the distinctive double row of kite-shaped plates rising vertically along its arched back and the two pairs of long spikes extending horizontally near the end of its tail. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International A foot (plural feet or foot; symbol or abbreviation ft or sometimes &prime – the prime symbol) is a non-SI unit Although a large animal, it was dwarfed by its contemporaries the giant sauropods. Sauropoda (sɔˈrɒpədə or the sauropods (/ˈsɔroʊpɒd/ are a suborder or infraorder of the Saurischian ("lizard-hipped" Some form of armour appears to have been necessary, as it coexisted with large predatory theropod dinosaurs, such as the fearsome Allosaurus and Ceratosaurus. Armor (or armour) in animals is external or superficial protection against attack by predators formed as part of the body (rather than the behavioural use of protective external Allosaurus (ˌæləˈsɔrəs is a Genus of large Theropod Dinosaur that lived 155 to 145 million years ago in the Late Jurassic Ceratosaurus (ˌsɛrətəˈsɔrəs meaning 'horned lizard' in reference to the horn on its nose ( Greek κερας/κερατος keras/keratos meaning

The hind feet each had three short toes, while each forefoot had five toes; only the inner two toes had a blunt hoof. All four limbs were supported by pads behind the toes. ^[3] The forelimbs were much shorter than the stocky hindlimbs, which resulted in an unusual posture. The tail appears to have been held well clear of the ground, while the head of Stegosaurus was positioned relatively low down, probably no higher than 1 metre (3. 3 ft) above the ground. ^[4]

Stegosaurus skull.

The long and narrow skull was small in proportion to the body. It had a small antorbital fenestra, the hole between the nose and eye common to most archosaurs, including modern birds, though lost in extant crocodylians. An antorbital fenestra is an opening in the Skull, in front of the eye sockets Archosaurs ( Greek for 'ruling lizards' are a group of Diapsid Reptiles represented by Modern birds and Crocodilians This group also The skull's low position suggests that Stegosaurus may have been a browser of low-growing vegetation. This interpretation is supported by the absence of front teeth and their replacement by a horny beak or rhamphotheca. Anatomy Stegosaurus --> Beaks can vary significantly in size and shape from species to species Stegosaurian teeth were small, triangular and flat wear facets show that they did grind their food. The inset placement in the jaws suggests that Stegosaurus had cheeks to keep food in their mouths while they chewed. ^[5]

Despite the animal's overall size, the braincase of Stegosaurus was small, being no larger than that of a dog. A well preserved Stegosaurus braincase allowed Othniel Charles Marsh to obtain in the 1880s a cast of the brain cavity or endocast of the animal, which gave an indication of the brain size. Othniel Charles Marsh ( October 29, 1831 &ndash March 18, 1899) was one of the pre-eminent Paleontologists of the 19th century who The endocast showed that the brain was indeed very small, maybe the smallest among the dinosaurs. The fact that an animal weighing over 4. 5 tonnes (5 US short tons) could have a brain of no more than 80 grams (2. This article is about the tonne or metric ton For other tons see Ton. The short ton ( S/T) is a unit of mass equal to 2000 lb (around 907 For other uses of the words gram or gramme see Gram (disambiguation. 8 oz) contributed to the popular old idea that dinosaurs were unintelligent, an idea now largely rejected. This article is about the unit of mass For the unit of force see Pound-force. ^[6]

Most of the information known about Stegosaurus comes from the remains of mature animals; however more recently juvenile remains of Stegosaurus have been found. One sub-adult specimen, discovered in 1994 in Wyoming, is 4. 6 metres (15 ft) long and 2 metres (7 ft) high, and is estimated to have weighed 2. 3 tonnes (2. 6 short tons) while alive. It is on display in the University of Wyoming Geological Museum. ^[7] Even smaller skeletons, 210 centimetres (6. 9 ft) long and 80 centimetres (2. 6 ft) tall at the back, are on display at the Denver Museum of Nature & Science.

Classification

Life restoration of Stegosaurus stenops.

Stegosaurus was the first-named genus of the family Stegosauridae. Known colloquially as stegosaurs the Stegosauria are a group of herbivorous Dinosaurs of the Jurassic and Early Cretaceous Periods It is the type genus, that gives its name to the family. In biology the phrase type genus is used differently depending on the nomenclatural ''Code'' that applies In zoological nomenclature, a type Stegosauridae is one of two families within the infraorder Stegosauria, with the other being Huayangosauridae. Known colloquially as stegosaurs the Stegosauria are a group of herbivorous Dinosaurs of the Jurassic and Early Cretaceous Periods Known colloquially as stegosaurs the Stegosauria are a group of herbivorous Dinosaurs of the Jurassic and Early Cretaceous Periods Stegosauria lies within the Thyreophora, or armoured dinosaurs, a suborder which also includes the more diverse ankylosaurs. The Thyreophora ("shield bearers" often known simply as "armored dinosaurs" - Greek: θυρεος, a large oblong shield like a door and Armor (or armour) in animals is external or superficial protection against attack by predators formed as part of the body (rather than the behavioural use of protective external Ankylosauria is a group of Herbivorous Dinosaurs of the order Ornithischia. The stegosaurs were a clade of animals similar in appearance, posture and shape, that mainly differed in their array of spikes and plates. A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor Among the closest relatives to Stegosaurus are Wuerhosaurus from China and Kentrosaurus from east Africa. Wuerhosaurus is a Genus of stegosaurid Dinosaur from the Early Cretaceous Period of China. China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National Kentrosaurus (meaning "pointed lizard" ˌkɛtroʊˈsɔrəs KEN-troe-SAW-rus, from the Greek kentron/κεντρον East Africa is the Easternmost Region of the African Continent.

Origins

Reconstruction of a Stegosaurus skeleton in the Senckenberg Museum in Frankfurt. The Senckenberg Museum in Frankfurt is the largest museum of natural history in Germany.

The origin of Stegosaurus is uncertain, as few remains of basal stegosaurs and their ancestors are known. Recently, stegosaurids have been shown to be present in the lower Morrison Formation, existing several million years before the occurrence of Stegosaurus itself, with the discovery of the related Hesperosaurus from the early Kimmeridgian. Hesperosaurus (meaning "western lizard" from Classical Greek, έσπερο-/hespero- "western" and σαυρος/saurus "lizard" The Kimmeridgian is a stage of the Late Jurassic Epoch. It spans the time between 155 ^[8] The earliest stegosaurid (the genus Lexovisaurus) is known from the Oxford Clay Formation of England and France, giving it an age of early to middle Callovian. Lexovisaurus was one of the first Dinosaurs from mid-to-Late Jurassic Europe, 165  mya to be discovered England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland This article is about the country For a topic outline on this subject see List of basic France topics. The Callovian is a stage on the Geologic time scale occurring 164

The earlier, and more basal genus Huayangosaurus from the Middle Jurassic of China (some 165 million years ago) predates Stegosaurus by 20 million years and is the only genus in the family Huayangosauridae. Huayangosaurus is a Genus of Stegosaurian Dinosaur from the Middle Jurassic of China. Earlier still is Scelidosaurus, from Early Jurassic England, which lived approximately 190 million years ago. Scelidosaurus (ˌsɛlɨdəˈsɔrəs meaning "limb lizard" from Greek skelos/σκελος meaning 'leg' and saurus/σαυρος England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland Interestingly, it possessed features of both stegosaurs and ankylosaurs. Emausaurus from Germany was another small quadruped, while Scutellosaurus from Arizona in the USA was an even earlier genus and was facultatively bipedal. Emausaurus is a Genus of Thyreophoran or armored Dinosaur from the Early Jurassic. Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. Scutellosaurus (meaning "little-shielded lizard" is a Genus of herbivorous Dinosaur that lived in North America around The State of Arizona ( is a state located in the southwestern region of the United States. These small, lightly-armoured dinosaurs were closely related to the direct ancestor of both stegosaurs and ankylosaurs. A trackway of a possible early armoured dinosaur, from around 195 million years ago, has been found in France. ^[9]

Discovery and species

Marsh's 1896 illustration of Stegosaurus. Note the twelve dorsal plates and eight tail spikes; Stegosaurus actually had 17 plates and just four spikes.

Stegosaurus, one of the many dinosaurs first collected and described in the Bone Wars, was originally named by Othniel Charles Marsh in 1877,^[10] from remains recovered north of Morrison, Colorado. The Bone Wars is the name given to a period of intense fossil speculation and discovery during the Gilded Age of American history marked by a heated rivalry between Edward Othniel Charles Marsh ( October 29, 1831 &ndash March 18, 1899) was one of the pre-eminent Paleontologists of the 19th century who The Town of Morrison is a Home Rule Municipality in Jefferson County, Colorado, United States. These first bones became the holotype of Stegosaurus armatus. A holotype is one of several possible Biological types A type is what fixes a name to a Taxon. The basis for its scientific name, 'roof(ed) lizard' has been thought to have been Marsh's initial belief that the plates lay flat over the animal's back, overlapping like the shingles (tiles) on a roof. Roof shingles are a roof covering consisting of individual overlapping elements A tile is a manufactured piece of hard-wearing material such as Ceramic, stone, metal or even Glass. A wealth of Stegosaurus material was recovered over the next few years and Marsh published several papers on the genus. Initially, several species were described. However, many of these have since been considered to be invalid or synonymous with existing species,^[11] leaving two well-known and one poorly-known species.

Valid species

Stegosaurus armatus, meaning "armoured roof lizard", was the first species to be found and is known from two partial skeletons, two partial skulls and at least thirty fragmentary individuals. ^[10] This species had four horizontal tail spikes and relatively small plates. At 9 metres (30 ft), it was the longest species within the genus Stegosaurus.

Fossil specimen of Stegosaurus stenops shown as it was found.

Stegosaurus stenops, meaning "narrow-faced roof lizard", was named by Marsh in 1887,^[12] with the holotype having been collected by Marshal Felch at Garden Park, north of Cañon City, Colorado, in 1886. A holotype is one of several possible Biological types A type is what fixes a name to a Taxon. For other similar names see also Canyon City. The City of Cañon City (ˈkænjən ˈsɪti The State of Colorado ( or chiefly by nonresidents) is a state located in the Rocky Mountain region of the United States of America. This is the best-known species of Stegosaurus, mainly because its remains include at least one complete articulated skeleton. It had large, broad plates and four tail spikes. Stegosaurus stenops is known from at least 50 partial skeletons of both adults and juveniles, one complete skull and four partial skulls. It was shorter than S. armatus, at 7 metres (23 ft).

Stegosaurus longispinus, meaning "long-spined roof lizard", was named by Charles W. Gilmore^[13] and known from one partial skeleton, from the Morrison Formation in Wyoming. Charles Whitney Gilmore (1874-1945 was an American paleontologist, who named Dinosaurs in North America and Mongolia, including the The Morrison Formation is a distinctive sequence of Late Jurassic Sedimentary rock that is found in the western United States which has been the most fertile source The State of Wyoming ( is a sparsely populated state in the western region of the United States. Stegosaurus longispinus was notable for its set of four unusually long tail spines. Some consider it a species of Kentrosaurus. Kentrosaurus (meaning "pointed lizard" ˌkɛtroʊˈsɔrəs KEN-troe-SAW-rus, from the Greek kentron/κεντρον Like S. stenops, it grew to 7 metres (23 ft) in length.

Nomina dubia (dubious names)

strata at Como Bluff

Stegosaurus ungulatus, meaning "hoofed roof lizard", was named by Marsh in 1879, from remains recovered at Como Bluff, Wyoming. Como Bluff is a long ridge extending east-west located between the towns of Rock River and Medicine Bow, Wyoming. Como Bluff is a long ridge extending east-west located between the towns of Rock River and Medicine Bow, Wyoming. The State of Wyoming ( is a sparsely populated state in the western region of the United States. ^[14] It is known from a few vertebrae and armour plates. A vertebra (plural vertebrae) is an individual Irregular bone in the spinal or Vertebral column ( aka ischis a flexuous and flexible column Armor (or armour) in animals is external or superficial protection against attack by predators formed as part of the body (rather than the behavioural use of protective external It might be a juvenile form of S. armatus,^[15] although the original material of S. armatus is yet to be fully described. The specimen discovered in Portugal and dating from the upper Kimmeridgian-lower Tithonian stage has been ascribed to this species. The Kimmeridgian is a stage of the Late Jurassic Epoch. It spans the time between 155 The Tithonian is the final stage of the Late Jurassic Epoch. It spans the time between 150 ^[1]

Stegosaurus sulcatus, meaning "furrowed roof lizard" was described by Marsh in 1887 based on a partial skeleton. ^[12] It is considered a synonym of S. armatus. ^[15] Stegosaurus duplex, meaning "two plexus roof lizard" (in allusion to the greatly enlarged neural canal of the sacrum which Marsh characterized as a "posterior brain case"), is probably the same as S. armatus. ^[15] Although named by Marsh in 1887 (including the holotype specimen), the disarticulated bones were actually collected in 1879 by Edward Ashley at Como Bluff, Wyoming. A holotype is one of several possible Biological types A type is what fixes a name to a Taxon. Como Bluff is a long ridge extending east-west located between the towns of Rock River and Medicine Bow, Wyoming. The State of Wyoming ( is a sparsely populated state in the western region of the United States.

Stegosaurus seeleyanus, originally named Hypsirophus, is probably the same as S. armatus. Stegosaurus (Diracodon) laticeps was described by Marsh in 1881, from some jawbone fragments. ^[16] Just as some consider S. stenops a species of Diracodon, others consider Diracodon itself to be a species of Stegosaurus. Bakker had resurrected D. Robert T Bakker (born March 24, 1945, in Bergen County New Jersey) is an American Paleontologist who helped reshape modern theories about laticeps in 1986,^[17] although others note that the material is non-diagnostic and likely synonymous with S. stenops. ^[11]

Stegosaurus affinis, described by Marsh in 1881, is only known from a pubis and is considered a nomen dubium. For the bone in many mammals often called the penis bone see Baculum The android pubic bone is the Ventral and Anterior In zoological nomenclature, a nomen dubium ( Latin for "doubtful name" plural nomina dubia) is a scientific name that is ^[15] It is possibly synonymous with S. armatus. ^[13]

Reassigned species

Stegosaurus madagascariensis from Madagascar is known solely from teeth and was described by Piveteau in 1926. Madagascar, or Republic of Madagascar (older name Malagasy Republic) is an Island nation in the Indian Ocean off the southeastern The teeth were variously attributed to a stegosaur, the theropod Majungasaurus,^[18] a hadrosaur or even a crocodylian. Majungasaurus (; meaning "Mahajanga lizard" is a Genus of Abelisaurid Theropod Dinosaur that lived in Madagascar Hadrosaurids or duck-billed Dinosaurs are members of the family Hadrosauridae, and include Ornithopods such as Edmontosaurus Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage

Other remains originally attributed to Stegosaurus are now considered to belong to different genera. This is the case for Stegosaurus marshi, which was described by Lucas in 1901. It was renamed Hoplitosaurus in 1902. Hoplitosaurus (meaning " Hoplite lizard" was a Genus of armored Dinosaur related to Polacanthus. Stegosaurus priscus, described by Nopcsa in 1911, is a synonym of Lexovisaurus. Lexovisaurus was one of the first Dinosaurs from mid-to-Late Jurassic Europe, 165  mya to be discovered ^[15]

Paleobiology

Animatronic Stegosaurus, Experimentarium, Copenhagen.

Stegosaurus was the largest stegosaur, reaching up to 12 meters (39 ft) in length and possibly weighing up to 5,000 kilograms (5. Known colloquially as stegosaurs the Stegosauria are a group of herbivorous Dinosaurs of the Jurassic and Early Cretaceous Periods 5 short tons). However, 7 to 9 metres was a more usual length. Soon after its discovery, Marsh considered Stegosaurus to have been bipedal, due to its short forelimbs. ^[19] He had changed his mind however, by 1891, after considering the heavy build of the animal. ^[12] Although Stegosaurus is undoubtedly now considered to have been quadrupedal, there has been some discussion over whether it could have reared up on its hind legs, using its tail to form a tripod with its hind limbs and browsing for higher foliage. ^[15] This has been proposed by Bakker^[20][17] and opposed by Carpenter. Robert T Bakker (born March 24, 1945, in Bergen County New Jersey) is an American Paleontologist who helped reshape modern theories about Kenneth Carpenter (born September 21, 1949 in Tokyo, Japan is a Paleontologist at the Denver Museum of Natural History and author ^[4]

Stegosaurus did have very short forelimbs, in relation to its hind legs. Furthermore, within the hindlimbs, the lower section (comprising the tibia and fibula) was short compared with the femur. The tibia, shinbone, or shankbone is the larger and stronger of the two Bones in the Leg below the Knee in vertebrates and connects For other uses see Fibula (disambiguation The fibula or calf bone is a Bone located on the lateral side of the Tibia The femur is the thigh bone In Humans, it is the longest, most voluminous and strongest Bone. This suggests that it couldn't walk very fast, as the stride of the back legs at speed would have overtaken the front legs, giving a maximum speed of 6–7 kilometres per hour (4–5 mi/hr). ^[5]

"Second brain"

Soon after describing Stegosaurus, Marsh noted a large canal in the hip region of the spinal cord, which could have accommodated a structure up to 20 times larger than the brain. This has led to the famous idea that dinosaurs like Stegosaurus had a 'second brain' in the tail, which may have been responsible for controlling reflexes in the rear portion of the body. It has also been suggested that this "brain" might have given a Stegosaurus a temporary boost when it was under threat from predators. ^[5] More recently, it has been argued that this space (also found in sauropods) may have been the location of a glycogen body, a structure in living birds whose function is not definitely known but which is postulated to facilitate the supply of glycogen to the animal's nervous system. Sauropoda (sɔˈrɒpədə or the sauropods (/ˈsɔroʊpɒd/ are a suborder or infraorder of the Saurischian ("lizard-hipped" Glycogen is a Polysaccharide of Glucose (Glc which functions as the secondary short term energy storage in Animal cells The nervous system is a Network of specialized cells that communicate information about an animal's surroundings and itself ^[21]

Plates

Front view of a Stegosaurus skeleton at the National Museum of Natural History.

The most recognizable features of Stegosaurus are its dermal plates, which consisted of 17 separate flat plates. These were highly modified osteoderms (bony-cored scales), similar to those seen in crocodiles and many lizards today. Osteoderms are bony deposits forming scales plates or other structures in the Dermal layers of the Skin. They were not directly attached to the animal's skeleton, instead arising from the skin. In the past, some palaeontologists, notably Robert Bakker, have speculated the plates may have been mobile to some degree, although others disagree. Palaeontology redirects here For the Scientific journal, see Palaeontology (journal. Robert T Bakker (born March 24, 1945, in Bergen County New Jersey) is an American Paleontologist who helped reshape modern theories about ^[22] Bakker suggested that the plates were the bony cores of pointed horn-covered plates that a Stegosaurus could flip from one side to another in order to present a predator with an array of spikes and blades that would impede it from closing sufficiently to attack the Stegosaurus effectively. The plates would naturally sag to the sides of the Stegosaurus, the length of the plates reflecting the width of the animal at that point along its spine. His reasoning for these plates to be covered in horn is that the surface fossilised plates have a resemblance to the bony cores of horns in other animals known or thought to bear horns, and his reasoning for the plates to be defensive in nature is that the plates had insufficient width for them to stand erect easily in such a manner as to be useful in display without continuous muscular effort. ^[23] The largest plates were found over the animal's hips and measured 60 centimetres (2 ft) wide and 60 centimetres tall. A centimetre ( American spelling: centimeter, symbol cm) is a unit of Length in the Metric system, equal to one hundredth The arrangement of the plates has long been a subject of debate but most palaeontologists now agree that they formed a pair of alternating rows, one running down each side of the midline of the animal's back.

Scutes, plates and skull of Stegosaurus, Denver Museum.

The function of the plates has been much debated. Initially thought of as some form of armour,^[19] they appear to have been too fragile and ill-placed for defensive purposes, leaving the animal's sides unprotected. ^[24] More recently, researchers have proposed that they may have helped to control the body temperature of the animal,^[22] in a similar way to the sails of the large carnivorous Spinosaurus or of the pelycosaur Dimetrodon (and the ears of modern elephants and jackrabbits). Spinosaurus (meaning "spine lizard" is a Genus of theropod Dinosaur which lived in what is now North Africa, from The pelycosaurs (from Greek πηλυξ pelyx meaning 'bowl' and σαυρος sauros meaning 'lizard' were primitive Late Paleozoic Dimetrodon (daɪˈmɛtɹəʊˌdɒn meaning "two measures of teeth" was a Predatory Synapsid (' Mammal-like reptile ' Genus The plates had blood vessels running through grooves and air flowing around the plates would have cooled the blood. ^[25] This theory has been seriously questioned,^[26] since the closest relative to the common plate-wielding species, Stegosaurus stenops, had low surface area spikes instead of plates, implying that cooling was not important enough to require specialised structural formations such as plates. Surface area is the measure of how much exposed Area an object has

Their large size suggests that the plates may have served to increase the apparent height of the animal, in order either to intimidate enemies^[13] or to impress other members of the same species, in some form of sexual display,^[24] although both male and female specimens seemed to have had them. Display is a form of animal behaviour, linked to survival of the species in various ways A study published in 2005 supports the idea of their use in identification. Researchers believe this may be the function of other unique anatomical features, found in various dinosaur species. ^[27] Stegosaurus stenops also had disk-shaped plates on its hips.

One of the major subjects of books and articles about Stegosaurus is the plate arrangement. ^[28] The argument has been a major one in the history of dinosaur reconstruction. Four possible plate arrangements have been mooted over the years:

Early reconstruction of Stegosaurus with plates lying flat along the back and tail spikes evenly distributed all over the body.

1. The plates lay flat along the back, like armour. This was Marsh's initial interpretation, which led to the name 'Roof Lizard'. As further and complete plates were found, their form showed that they stood on edge, rather than lying flat.
2. By 1891, Marsh published a more familiar view of Stegosaurus,^[12] with a single row of plates. This was dropped fairly early on (apparently because it was poorly understood how the plates were embedded in the skin and it was thought that they would overlap too much in this arrangement). It was revived, in somewhat modified form, in the 1980s, by an artist (Stephen Czerkas),^[29] based on the arrangement of iguana dorsal spines. Iguana is a Genus of Lizard native to tropical areas of Central and South America and the Caribbean first described by Austrian
3. The plates paired in a double row along the back. This is probably the most common arrangement in pictures, especially earlier ones (until the 'Dinosaur Renaissance' in the '70s). The " Dinosaur renaissance " was a small-scale scientific revolution started in the late 1960s which led to renewed academic and popular interest in Dinosaurs (The Stegosaurus in the 1933 film, King Kong has this arrangement. King Kong is the name of a fictional giant ape from the fictional Skull Island, who has appeared in several works since 1933 ) However, no two plates of identical size and shape have ever been found within the same animal.
4. Two rows of alternating plates. By the early 1960s, this had become (and remains) the prevalent idea, mainly because the one Stegosaurus fossil with the plates still articulated indicates this arrangement. An objection to it is that this phenomenon is unknown among other reptiles and it is difficult to understand how such a disparity could evolve.

Thagomizer (tail spikes)

Main article: Thagomizer

Thagomizer on mounted Stegosaurus tail. The thagomizer, or tail spikes, is an arrangement of four to ten spikes on the tails of particular Dinosaurs of the clade Stegosauria, of

There has been debate about whether the tail spikes were used for display only, as posited by Gilmore in 1914^[13] or used as a weapon. Robert Bakker noted the tail was likely to have been much more flexible than that of other dinosaurs, as it lacked ossified tendons, thus lending credence to the idea of the tail as a weapon. However, as Carpenter^[4] has noted, the plates overlap so many tail vertebrae, that movement would be limited. Bakker also observed that Stegosaurus could have maneuvered its rear easily, by keeping its large hindlimbs stationary and pushing off with its very powerfully muscled but short forelimbs, allowing it to swivel deftly to deal with attack. ^[17] More recently, a study of tail spikes by McWhinney et al. ,^[30] which showed a high incidence of trauma-related damage, confirms the spikes were indeed used in combat. Additional support for this idea was a punctured tail vertebra of Allosaurus into which a tail spike fit perfectly. ^[31]

Stegosaurus stenops had four dermal spikes, each about 60–90 centimetres (2–3 ft) long. Discoveries of articulated stegosaur armour show that, at least in some species, these spikes protruded horizontally from the tail, not vertically as is often depicted. Initially, Marsh described S. armatus as having eight spikes in its tail, unlike S. stenops. However, recent research re-examined this and concluded this species also had four. ^[11]

Diet

Stegosaurus tooth.

Stegosaurus and related genera were herbivores. However, they adopted a feeding strategy different from that of the other herbivorous ornithischian dinosaurs. Ornithischia (ɔrnɪˈθɪskiə) or Predentata is an extinct order of beaked herbivorous Dinosaurs The name ornithischia The other ornithischians possessed teeth capable of grinding plant material and a jaw structure capable of movements in planes other than simply orthal (i. e they could chew plants). This contrasts with Stegosaurus (and all stegosaurians), which had small teeth having horizontal wear facets associated with tooth-food contact^[32] and a jaw probably capable of only orthal movements. ^[15]

The stegosaurians must have been successful, as they became speciose and geographically widely distributed, in the late Jurassic. ^[15] Palaeontologists believe it would have eaten plants such as mosses, ferns, horsetails, cycads and conifers or fruits^[33] and swallowed gastroliths to aid food processing (due to the lack of chewing ability), in the same manner used by modern birds and crocodiles. Gastroliths (' Stomach stones' or ' Gizzard stones' are rocks, which are or have been held inside the digestive tract of an animal ^[34] Low-level browsing on grasses, seen in modern mammalian herbivores, would not have been possible for Stegosaurus, as grasses did not evolve until late into the Cretaceous Period, long after Stegosaurus had become extinct. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of

One hypothesised feeding behaviour strategy considers them to be low-level browsers, eating low-growing fruit of various non-flowering plants, as well as foliage. This scenario has Stegosaurus foraging at most one metre above the ground. ^[35] On the other hand, if Stegosaurus could have raised itself on two legs, as suggested by Bakker, then it could have browsed on vegetation and fruits quite high up, with adults being able to forage up to 6 metres (20 ft) above the ground. ^[5]

Behavior

Recent trackways from Colorado suggest that Stegosaurus lived in multi-age herds. One group of tracks is interpreted as showing four or five baby stegosaurs moving in the same direction, while another has a juvenile stegosaur track with an adult track overprinting it. ^[36]

Popular culture

Main article: Cultural depictions of Stegosaurus

Animatronic juvenile Stegosaurus, Tivoli, Copenhagen. Stegosaurus is among the most recognizable of Dinosaurs It has been depicted on film in cartoons comics as children's toys as sculpture and even was

One of the most recognizable of all dinosaurs,^[5] Stegosaurus has been depicted on film, in cartoons, comics, as children's toys, and has even been declared the State Dinosaur of Colorado in 1982. This is a list of US state dinosaurs in the United States, including the District of Columbia. The State of Colorado ( or chiefly by nonresidents) is a state located in the Rocky Mountain region of the United States of America. ^[37]

See also

• Othniel Charles Marsh
• Thagomizer

Footnotes

External links

• Walking With Dinosaurs - Stegosaurus
• Europe's First Stegosaurus Boosts Pangaea Theory